Conventionally, a solid bisphenol A (BPA) type epoxy resin or a novolac epoxy resin and a modified epoxy compound such as diethylenetriamine (DETA) adduct are used (blended) for a coating material capable of forming a coating film having excellent oil resistance, solvent resistance, chemical resistance and anticorrosive properties for use in the inner surface of a product carrier tank or the like. These coating materials can provide a coating film excellent in oil resistance, solvent resistance and chemical resistance. However, as they contain a relatively high molecular weight resin, they require a large amount of solvent in terms of coating workability and others, and it is difficult to make them a high solid type. If the amount of the solvent is reduced to make them a high solid type, oil resistance, solvent resistance and chemical resistance of the obtained anticorrosive coating film would be inferior to those of the conventional products without reduction of the amount of solvent.
If an epoxy adduct of an amine compound having a reduced ratio of an epoxy adduct is used in combination with a relatively high molecular weight resin to make them a high solid type, the coating material obtained has drying properties inferior to the conventional products. On the other hand, if a low molecular weight amine is used, the drying rate decreases.
Furthermore, a high solid type coating material using a modified polyamine such as cardanol or the like is available in the market. However, oil resistance, solvent resistance and chemical resistance of the coating film obtained are inferior to those of a coating material using a modified amine epoxy compound such as an adduct of diethylene triamine (DETA) and either a bisphenol A (BPA) type epoxy resin or a novolac epoxy resin.
JP-A-1995(H3)-275773 (Patent Document 1, corresponding to JP-B-2505301) discloses “a heavy-duty anticorrosive coated steel obtained by putting a coating layer on pretreated surface of the steel, wherein the coating layer material contains (a) a bisphenol type liquid epoxy resin having 2 or more epoxy groups in one molecule with an epoxy equivalent weight of less than 250, (b) a curing agent containing 10 to 100 parts by weight of an aliphatic polyamide amine or an epoxy compound modified with an aliphatic polyamide amine per 100 parts by weight of a modified amine of xylylenediamine or iso-phorone diamine with an epoxy resin, and (c) 20 to 65 wt %, as Pigment Weight Content, of a pigment”.
However, a coating film formed from the coating material for the heavy-duty anticorrosive coating of steel disclosed in the Patent Document 1 is inferior in oil resistance, solvent resistance and chemical resistance, and has a serious problem particularly in solvent resistance, such that a significant blister takes place in half a day when dipped in a solvent such as EDC, MEK or benzene at room temperature.
[Patent Document 1] JP-A-1995(H3)-275773 (corresponding to JP-B-2505301)